Lasers are useful in a multitude of hard and soft tissue dental procedures, including: removing decay, cutting, drilling or shaping hard tissue, and removing or cutting soft tissue. A tooth has three layers: the outermost layer is the enamel which is the hardest and forms a protective layer for the rest of the tooth. The middle and bulk of the tooth includes dentin, and the innermost layer includes pulp. The enamel and dentin are similar in composition and are roughly at least 70% mineral by weight, which includes carbonated hydroxyapatite, while the pulp contains vessels and nerves. Lasers at a wavelength in a range of 9.3 to 9.6 μm are well absorbed by the hydroxyapatite that is a significant component of tooth and bone, making such lasers efficient in the removal of hard tissue. The use of CO2 laser applications in dentistry has increased recently, e.g., with CO2 laser wavelength bands ranging between 9.3 and 10.6 μm. At wavelengths in the range 9.6 and 10.6 μm, phosphate absorption generally drops significantly, and thus dental lasers for the removal of hard tissue may be operated in the 9.3 to 9.6 μm wavelength range.
Lasers have been found to be useful in the removal of dental material without needing local anesthetic that is required when a similar procedure is performed with a drill. Further, lasers do not make the noises and vibrations that are associated with dental drills. At least for these reasons, it has been the hope of many in the dental industry that lasers may replace the drill and remove or at least reduce much of the discomfort, anxiety and fear from dental treatment.
In general, the optical power output of a laser beam can be described as the continuous power output of a continuous wave (CW) laser, or the average power output of a pulsed or modulated laser. The input laser power is measured in watts (sometimes referred to herein as “electrical power”), and the output laser power that irradiates a surface area (described e.g., in cm2) may be measured in watts/cm2 (sometimes referred to herein as “laser power,” or irradiance). The average power of a pulsed laser is the pulse energy multiplied by the laser repetition rate, where the pulse energy is in joules and the repetition rate is in hertz, or pulses per second. A maximum average laser power level for a pulsed laser can be calculated from pulse energy at the maximum laser repetition rate (pulses per second). The peak power of a pulsed laser can be described as the peak pulse energy divided by the pulse ON duration. For a given repetition rate, the pulse duty cycle is the percentage of the pulse cycle time/period that the ON duration of a pulse occupies.
Laser-mediated ablation of hard materials such as hydroxyapatite may require high peak pulse powers and short pulse durations (ON durations). The peak laser power required, in general, is a function of the laser power required to cleanly ablate hard dental tissue. The high peak laser power requirement often results in the use of an electrical power supply that may continuously provide the electrical power required for generating the laser pulse. For example, if for a particular application, the required laser power per pulse is 4 KW, a power supply capable of providing a continuous laser power output around 4 KW is traditionally selected. Such high-powered laser systems may also require cooling with a circulated coolant, generally using a refrigerated chiller, to remove heat from the coolant. The refrigerated chiller can add considerable volume and expense.
Various known techniques for supplying power to and/or cooling of laser-based dental treatment systems generally suffer from a number of disadvantages. For example, some known systems use a laser with a power rating that is significantly higher than that required for dental treatment applications, requiring an electrical power supply capable of providing the higher electrical power to such a laser. Some systems use a power source rated for continuous delivery of the power that is required to produce the peak laser output power. Such power source can be bulky, expensive, and may require cooling in addition to the laser-beam generator (also called laser). Furthermore, conventional techniques generally employ refrigeration systems in order to cool the heat produced by a laser with a high laser power rating.